It seems Facebook's new investor is keen to downplay its ties with "the hard man of Russia," an oligarch one critic called a "gangster and racketeer." How inconvenient, then, that said oligarch is reportedly buying up more shares.

Usmanov doesn't influence the company's management, Milner said. Digital Sky has a number of other investors, "including foreign ones," he said.

But it's hard to dispute that Usmanov is, as the Financial Timesput it, "among the biggest backers" of Digital Sky, which has just invested $200 million in the social network Facebook. Milner told Bloomberg he shares a 50 percent stake in the investment company with partner Gregory Finger. Other known investors include Goldman Sachs and Renaissance Capital.

Usmanov has just increased his stake in Digital Sky to 32 percent from 30 percent, according to a widely-cited story in the Russian daily Kommersant — owned, as it happens, by Usmanov, after the Russian government reportedly encouraged him to buy it.

With a minimum of five known investors in DST, the Oligarch's 32 percent is an impressive chunk.

Of course, his holdings present a minor PR headache for Facebook's benefactors at Digital Sky. But Facebook will need to get cozier with the Russian government if it wants to build its brand in Russia, as rumored. And in that effort, Usmanov seems like he'd be quite useful.